Pneumatically operated Shot Peening and Shot Blasting Machine

ABSTRACT

A pneumatically operated shot peening or blasting machine is designed to be convenient and mobile to be used to treat newly cut threads of oil tools in a contained and controlled manner. The machine uses compressed air and electric power to spray tiny Carbon Steel or Stainless Steel round balls to impart small indentation on the surface of the threads, or to clean and remove material from the surface of the tool. The indentations in shot peening puts the metal surface in compression creating stress zone and plastic deformation to relieve fatigue and prevent premature fractures and stress corrosion cracking. The inventive machine is designed to follow Shot Peening Standards such as MILS-13165B, J441, and AMS 2430 or other standards as apply.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional application No. 62/910,075, filed Oct. 3, 2019, the entire contents of which is incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

FIELD OF THE INVENTION

The invention is related to a shot peening or shot blasting machine and a specialized crescent shaped Y-nozzle used in shot peening or shot blasting. One specialized use is for shot peening of threads for oil tools such as the external and internal threaded ends of a section of pipe, by imparting small indentation or cavitation that create plastic deformation under the top layer to relieve fatigue, prevent premature failure as well as stress corrosion cracking. The invention enhances coverage in a single pass saving time and money as well as controlling and containing the shot, for a machine which is easier to use, safer to operate and more environmentally friendly. The machine can be mobile so it can be easily transported to a customer's work site or at the rig site for providing faster service.

BACKGROUND OF THE INVENTION

Shot peening is a cold working process in which spheroidal media (CS—carbon steel or SS—stainless steel) are projected to the surface of the tool causing compressive and residual stresses. The media hammers the surface causing small indentations that produce shallow, rounded overlapping dimples stretching the surface radially creating compressive stress zones. Shot blasting is used to clean the surface of the tool, removing material. The inventive machine can be used for either shot peening or shot blasting.

Fatigue damage evolves progressively under cyclic stresses and strains at levels lower than the elastic limit of the material and results in cracks that initially can be difficult to detect. Under adverse situations and if not detected, such cracks can develop rapidly and cause sudden and brittle failure in structures. Fatigue damage emanates at sites where geometric changes give rise to stress concentration, this makes fatigue the most critical failure criterion in down-hole tools or pressure equipment used in the oil and gas industry. The shot peening process therefore has been used in improving fatigue properties, stress corrosion cracking, last but not least mitigating residual stress. The residual stress based methods mainly rely on either removing the tensile residual stresses or even introducing compressive residual stress which delays the formation and development of fatigue cracks.

Current single nozzle systems are either fixed, requiring a machine to rotate the pipe or use a manually held nozzle which can be very difficult to operate, to direct the shot to uniformly cover the area to be treated and which allow the shot to bounce all over the area, which can be dangerous to the operator and which is environmentally unfriendly.

BRIEF SUMMARY OF THE INVENTION

The inventive machine (called the SPM-7) can perform both Shot Blasting and Shot Peening of both ID and OD of the pipe or tubular threads with the help of a Y-Nozzle connected to a lance which can rotates clockwise or counter clockwise. The machine has the capability to adjust the lance to align with the center of the pipe as well as the speed and direction of rotation. This unique capability allows the machine to operate in the field where adjusting the heavy tubular pipe on the rack may not easy.

The pneumatic motorized lance cart can be pneumatically operated to move up and down to ensure that the diameter of the pipe is at equal distance from both nozzles. The cart moves back and forth over the entire length of the thread or the section intended for blasting or peening. The Cart moves back and forth between the two limit switches that can be adjusted depending on the area to be peened (or blasted). The nozzle keeps rotating in a continuous circular motion between 0-9999 passes or adjusted as per client's specifications.

The invention is a shot peening or shot blasting machine having a source of compressed air and a lance for carrying spheroidal media, which is connected to the source of compressed air and which is connected to a device for rotating the lance at a predetermined adjustable speed, the device also able to move forwards and backwards between two adjustable predetermined positions (limit switches). The nozzle is connected to the lance, for directing the spheroidal media onto an axial length of the tool defined by the two adjustable predetermined positions. The nozzle and the axial length of the tool to be treated are contained within a shot media container. The inventive process of shot peening or shot blasting is easier, safer and more environmentally friendly because the shot media is controlled and contained. The tool can be any desired tool, but one example is a pipe having a threaded end, either an externally threaded end or an internally threaded end.

The tool can be a length of pipe having an end with external threads extending a predetermined axial length and wherein the nozzle is constructed and arranged for splitting the spheroidal media into two streams so that external threaded end of the pipe can be impacted with the two streams of media simultaneously, preferably at points 180° apart to enhance coverage and provide 100% coverage in a single pass as the nozzle is moved by the device axially forward and back between the two adjustable predetermined positions, which are selected to correspond to the axial length of the external threads.

The tool can be a length of pipe having an end with internal threads extending a predetermined axial length and wherein the nozzle is constructed and arranged for directing the spheroidal media onto the internal threaded end of the pipe as the nozzle is moved by the device back and forth between the two adjustable predetermined positions, which are selected to correspond to the axial length of the internal threads.

Alternatively, the nozzle can be configured for both external threads using a split stream of media or for internal threads using a single stream of media by having three nozzle ends, two outside ends forming a Y-shaped crescent nozzle and a central end, and where the nozzle can be selectively configured between the split stream configuration for outside threaded shot peening or shot blasting and the single stream configuration for internal threaded shot peening or shot blasting. In the single stream configuration a boron carbide insert is inserted to direct the stream into the central nozzle end and the two outside ends are plugged. In the split stream configuration the central nozzle end is plugged and the two outside nozzle ends are unplugged to direct spheroidal media between a split stream configuration or a single stream configuration and wherein the split stream configuration is for shot peening or shot blasting an externally threaded end of the tool, and wherein the single stream configuration is for shot peening or shot blasting an internally threaded end of the tool.

The spheroidal media can be carbon steel, stainless steel, glass and ceramic media, or any commercially available shot media. The size of the media can be any commercially available size, but is typically sized 0.18 mm, 0.28 mm, 0.42 mm, 0.58 mm, 0.71 mm and 0.84 mm in diameter. The machine has an adjustable volume of compressed air which is typically between 81 CFM (cubic feet per minute) to 196 CFM. The pressure can be adjusted anywhere from 30 psi to 120 psi to achieve the desired intensity.

The lance speed of rotation can be varied but it typically 20 rpm and a variable speed electric motor can be used to control the rotation. The cart speed can also be varied but is typically set to cover a meter in 8 seconds (1/8 meters per second). A variable speed electric motor can be used to move the lance back and forth, which is typically carried by a lance cart having wheels, and which can move between the two limit switches. The vertical height of the lance can be varied using a pneumatic lifting device so align the lance with the central axis of the tool to be treated, which is typically a threaded pipe.

The crescent shaped Y nozzle is comprised of several parts, including a Y-block, a pair of nipple fittings, a pair of banana nozzle fittings, a pair of reducer fittings and a pair of blast nozzle end pieces. The blast nozzle end pieces can be configured to vary the angle of spay from 45, 60, 90 Degrees as well as 135 Reverse Degrees. The Y-block can be of any size ranging from 3 inches to 36 inches, measured across the two ends of the Y-block. The angle of incidence between the two ends of the Y-block can also vary from 22.5° to 120°, to vary the distance between the blast nozzle end pieces.

The machine has a control which allows for controlling the number of passes the machine makes, whether the lance cart moves continuously or is stopped at a desired position for a desired length of time, the speed at which the lance rotates, and the speed at which the lance cart moves.

The used shot media can be recycled by arranging a bucket system below an opening in the shot media box (also called the peening box) to capture the used shot, screen it to remove the broken shot and transport the shot back to the blast pot.

The two stream nozzle is Y-shaped with the two ends of the Y forming a curved crescent shape.

The junction point where the shot is split into multiple streams can be reinforced with a harder metal, such as tungsten carbide to length the lifetime of the nozzle.

An alternative embodiment can use a fixed (non-rotating lance) which still splits the stream to provide 100% uniform coverage in a single pass while containing the shot in a shot box, by rotating the pipe to be treated. Another alternative embodiment could move the pipe to be treated axially rather than moving the lance using a lance cart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the inventive machine.

FIG. 2 is a another view of the inventive machine.

FIG. 3 is a back view of the inventive machine.

FIG. 4 is a top perspective view of the inventive machine.

FIG. 5 is a view of the control unit for the inventive machine.

FIG. 6 is a view inside the media box showing the nozzle and threaded pipe to be treated.

FIG. 7 is a view inside the media box showing the nozzle rotated to a different position.

FIG. 8 is a view inside the media box showing another view of the nozzle and threaded pipe to be treated.

FIG. 9 is a view inside the media box showing the nozzle and pipe to be treated, with the nozzle advanced as far forward as it can reach.

FIG. 10 is a schematic view of the crescent shaped Y-nozzle.

FIG. 11 is another schematic view of the crescent shaped Y-nozzle.

FIG. 12 is a view of an embodiment of the Y-nozzle.

FIG. 13 is a view of another embodiment of the Y-nozzle.

FIG. 14 is a view of another embodiment of the Y-nozzle.

FIG. 15 is a view of a three way embodiment of the Y-nozzle.

FIG. 16 is another view of a three way embodiment of the Y-nozzle.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.

For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated.

Referring now to FIGS. 1-5, the inventive shot peening or shot blasting machine is shown generally at 10. The machine is carried by a cart 12 which has wheels 14 to make the inventive machine portable and easy to transport to any desired location. The cart 12 has top rails 16 on which a motorized wheeled lance cart 18 can move back and forth between two limit switches 20. The lance cart carries a lance 22 which extends into a media box 24 (also referred to as a peening box) and which has a nozzle connected to it (best seen in Fig. ??). A tool to be treated, typically a pipe having either an external threaded end or an internal threaded end, extends through the back wall of the media box 24 (best seen in Fig. ??) so that the axial length of the tool to be treated is inside the media box 24. The media is contained in a blast pot 26 which feeds the media into the lance 22 using compressed air to move the shot media down the lance to the nozzle to treat the tool inside the media box. This provides a controlled and contained environment to make the treatment easier and safer for the operator, as well as more environmentally friendly. The lance 22 can be rotated at any desired speed, such as 20 rpm by the electric motor and gear assembly 28. The lance cart is moved backwards and forwards by the cart motor 30 at any desired speed, such as 0.125 meters per second. A control unit 32 is operatively connected to the motor 28 and motor 30 to control the rotation speed of the lance 22, the speed of the lance cart 18 and to control the number of passes back and forth that the machine will perform, as well as whether the lance cart 18 will move continuously or be programmed to stop at a desired location for a desired length of time.

FIGS. 6-9 shows a view inside the media box, which is normally closed to contain the shot media and prevent it from bouncing around and potentially hurting the operator. The lance 22 is connected to a nozzle shown generally at 34. Nozzle 34 can be switched out to perform different functions, for example one type of nozzle can be used to treat external threads and a second type of nozzle can be used to treat internal threads. Nozzle 34 shown in FIG. 6 is a crescent shaped Y-nozzle having a Y-block 36, which splits the shot media into two streams of shot. Each end of the Y-block has a nipple 38, a banana nozzle 40, a reducer 42 and a blast nozzle end 44, which has an opening 46 which can deflect the shot at any desired spray angle such as 45, 60, 90 degrees as well as 135 reverse degrees. The Y-block 36 can be of any size ranging from 3 inches to 36 inches, measured across the two ends of the Y-block. The angle of incidence between the two ends of the Y-block can also vary from 22.5° to 120°, to vary the distance between the blast nozzle end pieces 44. The nozzle shown in FIG. 6 is for treating external threads (or external surfaces) and is rotated by the lance so that the two streams of media are directed onto the threads from 180° apart, simultaneously, to achieve 100% uniform coverage of the threaded area to be treated in a single pass. A pass is defined as the nozzle moving axially forward and then backwards to treat the entire length of the threaded end of the pipe 48, with the thread axial distance being set with the two limit switches 20. The control unit 26 can be programed to perform multiple passes, from 1 to 9999, as desired.

Internal threads (not shown) can be treated by picking a small enough crescent shaped Y-nozzle so the blast nozzle ends 44 can both fit into the inside diameter of the pipe, and by rotating the blast nozzle ends 44 to face outwards rather than inwards. Alternatively a single stream nozzle can be connected to lance 22. As will be discussed further below, another alternative nozzle embodiment is a three way nozzle which incorporates the functionality of both the split stream configuration of the crescent shaped Y-nozzle as well as the single steam nozzle configuration into a single nozzle design.

FIGS. 10 and 11 show a close up view of the crescent shaped Y-nozzle and its parts. FIG. 12 shows an embodiment with longer Y sections and FIG. 13 shows an embodiment with shorter Y sections.

FIG. 14 shows an alternative embodiment in which the junction point which splits the media stream is reinforced with a tungsten carbide plug section 50 to extend the useful life of the nozzle.

FIGS. 15 and 16 show an alternative embodiment of the nozzle in which a three way nozzle is provided. The two ends 52 and 54 are the ends of the Y-shaped nozzle, with the addition of a central end 56. This nozzle design can be configured for either a split stream mode or a single stream mode. In the single stream mode (shown) a boron carbide insert 57 directs the shot media into the central nozzle end 56, and the ends 52 and 54 are plugged with plugs 58. Center end 56 has a blast nozzle end 44 (not shown) which extends into the inside of the pipe to treat the internal threads. In the split stream mode, the boron insert 57 is removed, plugs 58 are removed and the end 56 is plugged.

Operation of the Inventive Machine

Prior to setting machine for Shot Peening of parts, the operator first adjusts the air regulator and media flow rate on the blast pot. The cart on the machine is adjusted up or down by pneumatic pressure to ensure the Crescent Y-Nozzle is in the center of the tool. The to and fro movement of the cart is adjusted between the two limit switches according to the length of the thread that is to be peened. Based on the OD of the tubular the angle of incidence is adjusted on the Y-Nozzle. Once everything is adjusted the number of passes are set on the counter. The blast pot is turned on and machine is operated by a simple push of a button. After completion of the set passes the machine automatically stops. Once the verification of the coverage is determined the process is complete. The machine is simply moved to the next tool and process continues with much ease saving both time and money. Machine has an emergency stop button that shuts down the entire system by simple touch of the red button.

Intensity is determine by attaching An Almen Gage holder to the dummy part that is then Shot Peened at different time intervals (T) to determine the Arch Height, which results in figuring out the saturation curve.

Improvement Over Existing Equipment:

The machine is mobile and a self-contained unit that can be used both in the shop or the field. Based on the customer's specification the machine (SPM-7) can be adjusted to accommodate the following parameters. The Size of the Shots (0.18 mm, 0.28 mm, 0.42 mm, 0.58 mm, 0.71 mm, 0.84 mm, the Type of the Media, Adjustable Volume between 81 CFM to 196 CFM, Pressure between 30 Psi to 120 Psi to achieve desired intensity, Variation of angle of spay from 45, 60, 90 Degrees as well as 135 Reverse Degrees, Uniform Rotation of the lance in circular motion to enhance coverage while achieving uniform compression.

The machine can perform both ID and OD Shot Peening by simply replacing the Crescent shaped Y-Nozzle (for external threads) with a Hollow Blast Junior nozzle (for internal threads), or the inventive three way nozzle can be used, which allows a single nozzle to be used with both external threads and internal threads.

Coverage

Coverage is related to the benefit realized in achieving fatigue strength enhancement which results in preventing stress corrosion cracking. However the benefit of peening are realized by additional factors such as intensity and media selection including the size and hardness of the media.

Coverage is defined as percentage of the area exhibiting dents as percentage of the total area being considered. For example, coverage of 98% is to be considered 100% due to difficulty of measuring a small area. In order to achieve additional coverage such as 150% or 200% additional time exposure (T) is required. With its dual nozzle spray pattern the SPM-7 is capable of achieving 100% coverage in a single pass.

Peening Method

Shot Diameter may range from 0.0254 mm to 0.0762 mm, or from 0.127 mm to 0.254 mm, or 0.508 mm, or 0.762 mm to 1.016 mm, 1.27 mm to 1.524 mm, or 1.778 mm to 2.032 mm, or 2.286 mm to 2.54 mm, or greater. These media sizes are standard in the industry, however the bore size of Cresent Shaped Y—is designed according to the size of the media, intensity and coverage required.

The machine configuration can be changed with special fixtures where the lance can operate vertically or horizontally rotating on its axis. The rotation of the lance is achieved with the help of a motor, which in turn rotates either the Hollow Blast Junior Nozzle for the ID or the Crescent shaped Y-Nozzle for the OD moving to and fro based on the length of the thread uniformly peening the intended surface.

Shot Peening Machine SPM-7 can manage Air Flow rate between 81 CFM to 196 CFM. 

What is claimed is:
 1. A shot peening or shot blasting machine, comprising: a source of compressed air; a lance for carrying spheroidal media, which is connected to the source of compressed air and which is connected to a device for rotating the lance at a predetermined speed, the device also able to move forwards and backwards between two adjustable predetermined positions; a nozzle, connected to the lance, for directing the spheroidal media onto an axial length of the tool defined by the two adjustable predetermined positions; the nozzle and tool being contained within a shot media container; whereby the process of shot peening or shot blasting is easier, safer and more environmentally friendly because the shot media is controlled and contained.
 2. The shot peening or shot blasting machine of claim 1 wherein the tool is a length of pipe having an end with external threads extending a predetermined axial length and wherein the nozzle is constructed and arranged for splitting the spheroidal media into two streams so that external threaded end of the pipe can be impacted with the two streams of media simultaneously to enhance coverage and provide 100% coverage in a single pass as the nozzle is moved by the device between the two adjustable predetermined positions, which are selected to correspond to the axial length of the external threads.
 3. The shot peening or shot blasting machine of claim 1 wherein the tool is a length of pipe having an end with internal threads extending a predetermined axial length and wherein the nozzle is constructed and arranged for directing the spheroidal media onto the internal threaded end of the pipe as the nozzle is moved by the device between the two adjustable predetermined positions, which are selected to correspond to the axial length of the internal threads.
 4. The shot peening or shot blasting machine of claim 1 wherein the nozzle is a three way nozzle which can be selectively configured to direct spheroidal media between a split stream configuration or a single stream configuration and wherein the split stream configuration is for shot peening or shot blasting an externally threaded end of the tool, and wherein the single stream configuration is for shot peening or shot blasting an internally threaded end of the tool.
 5. The shot peening or shot blasting machine of claim 1 wherein the spheroidal media is selected from the group consisting of carbon steel, stainless steel, glass and ceramic media.
 6. The shot peening or shot blasting machine of claim 1 wherein the spheroidal media shot size is selected from the group consisting of 0.18 mm, 0.28 mm, 0.42 mm, 0.58 mm, 0.71 mm and 0.84 mm diameter shot media.
 7. The shot peening or shot blasting machine of claim 1 wherein the machine has an adjustable volume of compressed air of between 81 CFM to 196 CFM.
 8. The shot peening or shot blasting machine of claim 1 wherein the machine has an adjustable pressure of compressed air of between 30 psi to 120 psi to achieve the desired intensity.
 9. The shot peening or shot blasting machine of claim 2 wherein the nozzle has two ends having blast nozzle ends which can be selected to adjust the angle of spray of the shot media from the group consisting of 45°, 60°, 90° and 135 reverse degrees.
 10. The shot peening or shot blasting machine of claim 1 in which the lance is rotated at 20 rpm to enhance coverage while achieving uniform compression and in which the lance is carried by a motorized lance cart which moves between the two predetermined positions at 0.125 meters per second.
 11. The shot peening or shot blasting machine of claim 1 wherein the machine has a pneumatic vertical height adjustment to adjust the lance and nozzle so it is centered on a tool axis.
 12. The shot peening or shot blasting machine of claim 2 wherein the nozzle directs the two streams simultaneously onto the tool at points 180° apart to achieve 100% coverage with a single pass.
 13. The shot peening or shot blasting machine of claim 1 wherein the device rotates the lance using an electric motor.
 14. The shot peening or shot blasting machine of claim 8 wherein the device uses an electric motor to move forwards and backwards between the two predetermined positions.
 15. The shot peening or shot blasting machine of claim 9 wherein the device includes a control device for setting the number of passes the machine makes between the two predetermined positions and the rotation speed of the lance.
 16. The shot peening or shot blasting machine of claim 1 wherein the machine is carried on a wheeled cart so the machine is mobile and can be taken to where tools need to be treated.
 17. The shot peening or shot blasting machine of claim 1 wherein the shot media container has an opening in the bottom which allows used shot media to be collected, screened to remove broken shot media and reused.
 18. A valve for shot peening or shot blasting, comprising: a section for carrying shot; a junction section having at least two split sections for splitting the shot into at least two streams of shot; rotatable end sections connected to each of the at least two split sections for directing the shot either inwards or outwards, whereby either an external surface of a tool can be shot peened or shot blasted, or an internal surface of a tool can be shot peened or shot blasted.
 19. The valve for shot peening or shot blasting of claim 18 wherein the junction section is Y-shaped having two split sections, with the two ends of the Y forming a curved crescent shape.
 20. The valve for shot peening of claim 18 in combination with a machine for shot peening or shot blasting, further comprising: a source of compressed air, which is connected to the section for carrying shot; spheroidal peening media which is directed by the compressed air through the section for carrying shot, and which is split into two streams by the Y-section.
 21. The combination of claim 20 further including rotation apparatus for rotating the valve to treat the threads of the pipe around the entire circumference of the pipe with the two streams of shot.
 22. The combination of claim 21 further including axial movement apparatus for moving the valve along a predetermined axial length of the pipe to be peened or blasted.
 23. The valve for shot peening or shot blasting of claim 18 wherein the junction section has three split sections, two outside Y-nozzle sections and one center section, and where a carbide insert can be inserted to selectively direct the shot media into the two outside Y-nozzle sections for treating external threads or to direct the shot media into the center section for treating internal threads.
 24. The valve of claim 23 wherein the junction point is reinforced where the splitting of the streams occurs to length the useful life of the nozzle.
 25. The valve of claim 24 wherein the junction point is reinforced with tungsten carbide.
 26. A shot peening or shot blasting machine, comprising: a source of compressed air; a lance for carrying spheroidal media, which is connected to the source of compressed air and which is connected to a device which move forwards and backwards between two adjustable predetermined positions; a nozzle, connected to the lance, for directing the spheroidal media onto an axial length of the tool defined by the two adjustable predetermined positions to treat the axial length of tool; a rotation device for rotating the tool; the nozzle and the axial length of tool to be treated being contained within a shot media container; whereby the process of shot peening or shot blasting is easier, safer and more environmentally friendly because the shot media is controlled and contained. 